1. Field of the Invention
The present invention generally relates to a motor. More specifically, the present invention relates to a motor that uses permanent magnets.
2. Background Information
A permanent magnet motor having a forward salient pole characteristic is known as an electric motor for use as a drive motor in electric vehicles. This permanent magnet motor has a so-called forward salient pole characteristic wherein a d-axis inductance is larger than a q-axis inductance. Such a permanent magnet motor having a forward salient pole characteristic is superior to a motor having a reverse salient pole characteristic with respect to achieving both high torque performance and high rotational speed performance with the same motor. One example of this kind of permanent magnet motor is disclosed in Japanese Laid-Open Patent Publication No. 2006-081338 (entitled “Rotor of Rotary Electric Machine”).
In the permanent magnet motor having a forward salient pole characteristic as in disclosed in Japanese Laid-Open Patent Publication No. 2006-081338, the forward salient pole characteristic of the d-axis inductance being larger than the q-axis inductance is achieved by reducing the q-axis inductance. The q-axis inductance is lowered by adopting an interior permanent magnet (IPM) structure and forming a plurality of slits on a radially outward side of the permanent magnets. The slits are arranged to be parallel to the magnetic flux.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved motor. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.